This invention relates generally to furnaces and, more particularly, to an air baffle for diverting air over a particular portion of a furnace heat exchanger for preventing hot spots.
Residential furnaces typically include a plurality of heat exchanger panels or cells arranged in parallel relationship, with the air to be heated being circulated by a blower so as to pass between the panels and over the surfaces of the panels, to be heated. The panels have associated burners for heating the air within the panels, and an inducer may be employed to draw the heated air through the panels and discharge them to a flu.
One form of heat exchanger that is commonly used in such furnaces is a so-called clamshell heat exchanger, wherein two stamped metal shells are fastened together to form a single panel having a plurality of serpentine passages, or passes, through which the hot gases can be caused to flow. Thus, a burner heats the air at an inlet end thereof, and the hot gases pass through successive passes and finally come out of the exit end of the panel to eventually be discharged to the flu. As the gases pass from the inlet to the exit end of the panel, they are cooled by the air being circulated over the surface of the panel. Thus, the gases in the first pass are at substantially higher temperatures than those downstream thereof, and care must be taken to prevent the occurrence of excessive temperatures. In particular, hot spots are most likely to occur in the vicinity between the first return bend and the second pass. These hot spots cause not only exposure to high temperatures, but also to undesirable temperature gradients that can cause excessive strain levels in the material of the heat exchanger structure and may eventually lead to failure.
It is therefore an object of the present invention to provide an improved furnace heat exchanger apparatus.
Another object of the present invention is to provide a heat exchanger apparatus with reduced thermal stress.
Yet another object of the present invention is the provision for maintaining the temperatures on the surface of a heat exchanger panel within acceptable limits.
Still another object of the present invention is the provision in heat exchanger apparatus for lowering both the peak temperatures and the temperature gradients on the surface of a heat exchanger.
These objects and other features and advantages become more readily apparent on reference to the following descriptions when taken in conjunction with the appended drawings.
Briefly, in accordance with one aspect of the invention, a baffle structure is positioned between a pair of heat exchanger panels, with the location being such that the baffle tends to divert a portion of the circulated air over the localized surface where hot spots are likely to occur on the heat exchanger panel. The increased air flow over that surface reduces both the peak temperatures and the temperature gradients that occur.
In accordance with another aspect of the invention, the baffle is an elongate, relatively flat member that is positioned near the transition between the first return bend and the second pass, and extends substantially parallel with the second pass. The baffle causes circulating air to be diverted over the localized area of each of the adjacent panels, which area would otherwise be susceptible to hot spots.
In accordance with another aspect of invention, a plurality of baffles are provided, with the baffles being integrally combined with a rear wall bracket or baffle, which is installed for the purposes of both channeling the flow of circulation air away from the rear wall and toward the heat exchanger panels, and maintaining proper spacing between adjacent heat exchanger panels. The bracket is fastened to the furnace casing and includes spacer portions that engage the panels on either side thereof, as well as baffle portions which extend into positions between, but do not engage, adjacent heat exchanger panels.